Field emission devices (cathodes) serve as a source of electrons, and are of use in various scientific and medical fields. Such applications may include sterilization systems, gas ionization systems (e.g., mass spectrometry), klystrons, flat-panel displays, cathode ray tubes, scanning electron microscopes, transmission electron microscopes, and energy dispersive x-ray analysis, to name a few. As another example, by radiating a target with an accelerated electron beam, field emission devices may be used as a source of x-rays. In many applications, it is desirable that field emission devices provide a relatively high electron flux with relatively low power consumption, are stable with a long life, and which may be efficiently manufactured.